A discussion about global warming

This discussion thread about global warming is posted here not only because it is interesting, but also to get your analysis of this debate.

Background

The comments on the climate change posts on the FM site are similar to those on the posts about the “Dude, Where’s my Recession” meme (here and here). That meme was a response to exaggerated media pessimism about the economy. But despite 100+ comments, no specific examples could be produced to support the theory (which I limited to just the print media, to eliminate the “Once I saw on TV” anecdotal evidence).

Here, and in the other posts about climate change on the FM site, we have something similar. Posts with specific critiques of the case for anthropogenic global warming (AGW), both evidentiary and methodological. The 160+ comments giving rebuttals almost totally ignore the case for skepticism presented, usually just repeating that AGW deserves a massive public policy response.

A fine example of this is the post about Michael Crichton’s January 2003 speech at the California Institute of Technology (here), which criticized relying on the consensus opinion of science as a guide for public policy. Several of the comments gave rebuttals relying on the consensus of scientists’ opinion (showing no awareness of the incongruity involved, perhaps because they were writting rebuttals to a text they had not read).

This thread

This post contains an extended dialog lifted from the comments of the two most recent posts about AGW on this site. The pro-AGW representative is Keith Eric Grant.

There are 3 reasons this dialog is given as representative of the many comments on the FM site in support of AGW theories. First, Grant’s background (see below). Here is an excerpt from the bio on his company’s website.

Keith holds a BS in physics from San Jose State University and an MS and Ph.D. in Applied Science (School of Engineering) from the University of California, Davis. He is now the founder, senior research scientist, and science writer for Ramblemuse Associates. He worked for the Lawrence Livermore National Laboratory (LLNL) from June 1972 until May 2008. His scientific experience includes atmospheric chemistry and and transport modeling, radiation transport, inverse problems, aerosol microphysics and optical properties modeling, nonlinear solver development and applications, climate modeling, satellite data analysis, user consulting, and signalanalysis. … He is a member of the American Geophysical Union (AGU), the Society for Industrial & Applied Mathematics (SIAM), the American Massage Therapy Association (AMTA), the Northern California Science Writers Association (NCSWA), and the National Association of Science Writers (NASW).

In terms of relatively basic physics, there are good reasons to expect that anthropogenic climate change will occur. Human contributions of CO2 into the atmosphere can be estimated from source inventories. CO2 from fossil fuel burning is also depleted in Carbon-14, creating a tracer that is consistent with measurements of isotopes. The estimate of 3.7 W/m2 of forcing (i.e. before any feedbacks) from doubling CO2 isn’t controversial. Quite simply, less heat is initially emitted by the planet to space and it has to come back into balance. A feedback has to involve some increase in temperature to drive other changes. Other changes include increased water vapor (also a greenhouse gas), increased cloudiness, and changes in surface reflectivity. High clouds trap more infrared radiation; low clouds reflect more sunlight back to space. The non-temperature changes imply changes in rainfall and in the geographic and seasonal distribution of rainfall. Balancing energy does not imply no anthropogenic change.

Climate models are physics process models. They represent, to the best implementable approximation, the state of knowledge of the atmosphere. The validity of the various pieces and parts get tested against more exact representations and against data. The documentation and discussion is available, if strewn through decades of literature. Documentation of the physical basis of models is also available. Most research is blind in the sense that it focuses on improving the representation of physical processes. You don’t know the effects on climate model results until much later. Scientific consensus does not mean arbitrary agreement. It means that a lot of scientists in different areas of expertise have both cross-checked (and argued) with each other to the point that they view the treatment is reasonable and appropriate.

Regional climate variations can occur as a result of transport of heat, without a change in the global heat balance. Global change occurs when some factor, anthropogenic or not, changes that balance.

Given an energy forcing from human activities, the best bet is that it will create observable changes in temperature and precipitation — not just in averages but in regional patterns.

The open question is how we limit and mitigate change and how we ensure that the costs are not separated from the benefits. So part of the question arises in how to do the accounting so that costs to the commons are include.

Part of mitigation requires addressing limitations in how human social systems respond and in keeping a functional relationship between observation, including predictive ability, and action. Whereas nomads in the distance past may have responded to north or south migration of rainfall by changing location, people these days get excited by groups of people crossing borders. Climate change can further stress systems of sustenance already under stress. Darfur may be an example, as suggested in an article by Stephan Faris.

A change in rainfall or growing season may mean that a hybrid crop is no longer appropriate in the region for which it was developed. Moving the growing area may involve both changes in terrain and soil-type.

A change in sea-level may mean that some island states become uninhabitable and some current coast cities become to susceptible to weather extremes. The residents of the Maldives are currently shopping for new property.

The bottom line is not that the sky is falling, but that not planning for anthropogenically induced climate change is as unwise as not observing economic and political feedbacks. Missing the opportunity to both plan and mitigate effectively, has its own economic costs and it’s own potential effects on global security. Everything has its indirect costs, including the burning of fossil fuels.

(1) “Documentation of the physical basis of models is also available.”

Validation of large climate models requires days or weeks of work by a multi-disciplinary work, esp. if the models are poorly documented code. The availability of the data is nice, but has anyone funded a 3rd party review of these models? That should be a prerequiste for the introduction of their output as evidence into the public policy debate.

(2) The story about the Maldives was also fascinating, noting that the population doubled in the past 20 years from 200 to 400 thousand. What was it during the previous warm spell, the Medieval Optimum, 800 – 1300 AD? Per the Population Statistics website, their population was 50 thousand in 1900 and 30 thousand in 1880. Probably a lot more room per person, even when sea levels were higher. Natural climate cycles can become painful when the population grows 13-fold on a small island.

An interesting list of skeptic’s complaints, but perhaps missing an essential point. Why, if we change the energy balance of the earth should we take as the default assumption that the manner in which the Earth comes back into balance will have little or no consequence?

The physics of the forcing itself are not that complicated. If one is willing to look at only a global average, Manabe and Wetherald provided an answer with a reasonably simple model back in 1967.

You make much of the concept of consensus, but little of the vast published research literature that is the cause for much of the consensus. Atmospheric and oceanic science literature has a long history of publication — much more than any one person can keep up with. The physics that has gone into models has been examined and reexamined. One of the differences between modeling the Earth system and problems such as economics, is that it is inherently a problem of physics, albeit physics too complex to be able to do all details justice and impossible to measure all the details of input. That does not imply that the approximations possible are meaningless.

A good example of this process of science, supposedly ignored, came in the 1990’s when Cess et al. published a study that clouds were “blacker” (i.e. absorbed more) than predicted by theory. Another example occurred when the eruption of Mt. Pinatubo provided an observational opportunityto measure surface temperature sensitivity to radiative changes. Such checking of understanding against observations is a continual process. There is not a simple reliance on models but a reliance on understanding of physics coupled with use of measurement. Yet ultimately, even when all the separate processes are understood, a model may be the only means of exploring the behavior of a complex system with many feedbacks.

In my prior comment I never said that skeptics disbelieve climate change, at least short of groups disbelieving that the world is old enough to have undergone climate change. It was also intentialal that I referred to climate change rather than “global warming”. The warming is only one aspect, albeit a driving one, of the total feedbacks.

And skeptics certainly vary, from those who have legitimate arguments on a specific conclusion (and know the research background) to those who wander in from the side without bothering to gain background. There are equally people who make claims about “global warming” without understanding — sufficient to make my eyes roll.

The problem of detection of an anthropogenic effect from amid the noise is also a separate one from understanding the physics driving both weather and climate. Detection is, in principle, a matter of estimating the level of noise of a trendless system and then estimating the probability of the observed rate and magnitude of change assuming no anthropogenic effects.

I have known few scientist would are unwilling to talk to or work from a standpoint of improving what we understand about how the Earth responds to an energy imbalance. Given that a number of areas of science have become areas of bare survival under the stress of overcommitment of hours, I also well understand an unwillingness to work with those who have a different agenda than improved understanding and even less understanding of the background. I know of few Earth scientist who entered the area from an eagerness to argue with skeptics. Most simply have a driving obsession with figuring out home things work and improving understanding a bit. I suspect that in most areas of human endeavor, those entering a group with the intention of showing how its all being done wrong rather than improving what’s already being done will find their welcome self-limited.

Again, however, increasing the concentration of greenhouse gasses implies creating an energy imbalance that the Earth will respond to. If the weight of 50+ years of atmospheric physics is deemed to provide the wrong answer for the nature of that response, it’s certainly interesting to consider what else will provide a better prediction of how the feedbacks will play out.

For those interested in the physics, something like Piexoto and Oort or Rayner’s Dynamic Climatology are reasonable starts. Perhaps those skeptical of the science basis can learn more about it while I can take more measure of skeptic’s comments.

Unfortunately, what this mode of a priori discounting of any need for prevention and mitigation seems to preclude is discussion of realistic politicaland social responses that might prove cost effective. Climate feedback to human activities is unlikely to be either a zero or one with nothing in between. That, unfortunately seems to be where the discussion goes, however.

Reply: There is almost nothing here to reply to. You must realize that this comment displays most of the characteristics I discuss in my post. You show no evidence that you have read the skeptics work (which does not consist of “complaints”), nor do you mention any of the specifics elements in their case. Your rebuttal essentially discusses a position you have made up, which I guess makes it easy to win a debate (since you are playing both sides).

This statement is esp bizarre: “what this mode of a priori discounting of any need for prevention and mitigation…” This is almost the mirror image of the skeptics actual position.

There is indeed more to models than just physics, since all tractable model require approximations. There is a saying that a model should not be more complex than necessary. Neither, however, should it miss important aspects. Between those two lives a lot of tacit knowledge of the modeler.

One other comment I did note: “The concerns about changes in global mean temperature are based on the assumption that the earth is currently at the optimal temperature and that variations over years (unlike variations within days and years) are undesirable.”

This is not necessarily the assumption. I believe that it is more that biological distributions of species and our own social and food production systems are adapted to the current regime. If we create relatively rapid climate change (which involves more than just temperature), then we need be prepared to handle a range of adjustments that cross many national boundaries. It’s not at all clear that we have the social/economic organization to accomplish this. It also requires policy and leadership with timescales beyond 4 years.

The Wegman report also makes an interesting read, BTW.

Reply: Your re-statement is equivalent (with more detail) to the original version in the E&E paper. Optimal means “best” or “most favorable” — the unstated assumption being “for us.” Or in your words, “the current regime.” Otherwise the word has no meaning, except perhaps to a theologian as “best in the sight of God”.

Fabius, short of invoking a deity, there can be a distinction. Most favorable/optimal in inherent ability to support life may be different from where we are now — but the transit between the two might be rough, requiring some destruction and resynthesis of current boundaries and infrastructure.

Reply: That’s a valid point. It seems a theoretical one, as you are describing a largely non-existent body of pro-AGW work (both by scientists and laypeople) that make your precise distinction. The Green-Arnstrong phrasing better described the body of actual writings on the subject at this time.

Pete, Climate models and weather models are, in terms of physics, converging. One can’t predict weather beyond about a week, because it involves matching particular storms in particular places starting from imperfect initial conditions and an approximate model. Climate, however, is essentially the long-term statistical envelope of weather. Thus it’s a matter not of timing, but of catching the mean and variability of circulation and precipitation. Tim Palmer recently wrote Predictability of Weather and Climate should anyone be interested.

Greg Panfile’s comment hits part of the issue. It is a relatively simple matter to calculate the energy forcing from greenhouse gases. That forcing is not particularly controversial. What complicates the matter is that heating from the initial forcing changes the amount of water vapor in the atmosphere, which is also a strong greenhouse gas. Water vapor change also leads to changes in clouds, which can either heat or cool depending on the altitude. Others, such as the Pielkes and Petr Chylek believe that other factors such as land use changes aren’t being fully considered. Roger Pielke, Sr. has his own Climate Science blog.

In constrast, the Climate Audit and the Wegman report (linked from the Audit) focus on problems in Mann’s analysis of paleoclimate data. The Wegman report notes that the data set “does not provide insight and understanding of the physical mechanisms of climate change” and that “What is needed is deeper understanding of the physical mechanisms of climate change”. In short, the data set is about detection of change. Pielke et al. are discussing mechanisms.

Reply: I agree on all points! What spins the debate out of control IMO is the poor temperature record of modern times — up to and including today; both ground, atmosphere, and satellite. Without reliable current data to anchor the debate, everything becomes a moving target. See the previous comment for a specific example of this.

Also note the Wegman and North reports validate many of the skeptics concerns about the historical temperature records created by the pro-AGW scientists use of proxy data. So we have poor data and limited understanding of the physical mechanisms. A weak basis for expensive policy action.

Admittedly, a lot could be done to better data quality. Policy and funding are often thin and inconsistent which coupled with parochialism in college departments (Wegman report notes that statisticians at same university weren’t consulted) doesn’t help. Gaps in funding for satellites, leading to delays in launching instruments, leading to lack of overlap in measurements also doesn’t help. This was a problem several year back in solar cycle monitoring. The solar cycle effects are not simply ignored, btw. People like Judith Lean have been looking and writing about them for years, including in Science.

To what does this refer? My only mention of solar cycles on this thread is “Many of the pro-AGW comments here discuss cartoon-like models of earth’s climate (co2 only), to show that AGW is obvious. These ignore important issues of magnitude and feedbacks, not to mention other factors (e.g., solar cycles). ” I doubt Dr. Lean (bio) has posted any comments on this site.

I suggest you look at sections 1, 2 and 3 on the FM reference page about Science, Nature, and Geopolitics. You will see that the FM site has 4 posts about the current solar cycle, lists 5 sites with current coverage, and links to 9 articles on the subject.

On a different note, re your statement “Policy and funding are often thin and inconsistent which coupled with parochialism in college departments…” NASA and NOAA claim to do rigorous quality control on the surface temperature data, a high priority system vital to climate-related public policy. However, events have shown this to be false (see this, for example). I doubt lack of funding is the problem, given the relatively tiny sums required.

FxConde, the Earth, ultimately, will not terribly care what the level of CO2 is. There have been times in the past in which the diversity of life dropped greatly, but eventually, the Earth moves on. The question as to “safe” depends on the definition of “safe for what?”. Perhaps Hansen is simply saying that beyond that mark humans will have to make accommodations for a climate change we produce. This would be based on the underlying physics, not measurements aimed at detection.

A change in the global annual mean temperature doesn’t speak to regional change, one of the points that Pielke makes. Warmer temperatures can mean longer growing seasons, more snowfall in some areas, or a crop of dryland wheat killed by heat before the rains come. It can also mean a winter snowpack that instead falls as rain and runs off in floods long before it’s needed in the middle of summer. The estimate of global temp. change for doubling CO2, without any other feedbacks is about 1.1 deg C. With other feedbacks, it ranges between 1.6-4.5 deg C with most bets in the 2-3 deg range. The water vapor bit was surveyed in an “Insight” series put out by Nature. That doesn’t say a thing about anybodies own backyard.

Reply: While I agree the remark about “the Earth” is silly rhetoric (something that pollutes both side of this debate), I suspect FxConde refers to the broad historical pattern. The Little Ice Age was a bad time for many northern hemisphere societies, due to repeated crop failures. The warmer “medieval optimum” was on the whole a better time, food-wise. Several noted agricultural experts have expressed concerns about the effect of possible cooling period, given the very low levels of global grain stockpiles (in terms of days-demand, or per capita demand).

Fabius, that comparison between the Little Ice Age and medieval optimum makes sense. A warmer global temperature might conceivably support more food production then we accomplish now. But than goes back to my earlier comments about being adapted to the present versus what might be “optimum” — there could still be adaptions in human systems and shifts in rainfall patterns between the two. Some tropical diseases and other pests could also find new ranges.

Recent warming years, whatever the immediate cause, have extended the range of pine beetles, first into British Columbia and then jumping into Alberta. Science writer Charles Petit did a profile on a person looking at the connection between bears and whitebark pines. A recent CBC news report says the infestation may be tapering off, only because the beetles have run out of food. Cold winters kill off the beetles, previously limiting their range.

None of this is unprecedented or the end of the world. Any choice, however, is going to have trade-offs. It’s the comments like one made some years back by a Republican Congressman, “Warmer? I wouldn’t mind a few airports being warmer in the winter.”, that reveal when decisions are made without having a clue or a care.

Reply: There are many questionable assumptions embedded in your comment about making “choices”.

That we understand climate processes sufficiently well to draw reliable conclusions.

That current changes are above the magnitude of “background” noise or natural variation in climate.

That we have the ability to affect these trends.

That we can do so at some possible cost.

Only the latter brings the element of choice into the picture. We are IMO a long way from that point in the decision-making process.

The beetle story is interesting, but then these days the path to government funding seems to require a link to climate change. Reading the general media it seems that all change results from climate change, including earthquakes.

I hadn’t realized when I wrote earlier about bark beetles, BTW, that they are featured in today’s NY Times.

In 1967, Manabe and Wetherald did a simple study on the energetics, using a radiative-convective model. If they assumed that absolute water vapor was constant, the got a 1.3 deg C change in global average temperature. If they assumed that relative humidity were constant, they got a 2.3 deg change. Both observationally and from consideration of how evaporation, convection, latent heat release, the temperature lapse rate, and radiation to space are tied together, the relative humidity assumption is more likely to be correct. Modern climate models don’t assume relative humidity, but in relating the variables listed above they come close to predicting constant relative humidity. Temperature changes following the Mt Pinatubo eruption also seem to satisfy this.

So, from fairly basic considerations, this order of temperature change is very feasible if not likely. This says nothing about geographic details or how the planet will distribute such change or about our ability to detect change from under the background of noise. The result, however, is neither trivial nor dumb-minded.

We make a choice whatever we do. Choosing not to choose is also a choice. I’m not suggesting what policy is possible, but that we do need to take the issue seriously enough to look at policy. Right now the southern part of California has been “infested” with fires, as central California has t-shirt weather. Whether anthropogenic or not, this is a climate variation event. Do we handle such events as isolated incidents or do we notice patterns and do more coordinated planning? As one level, this is the same kind of planning that should be done as to earthquakes or hurricanes. Do what we can to prevent damage, do what we can to mitigate damage, and have some preparation to handle people who need assistance or relocation. Look at the security considerations from what might occur in other countries.

Reply: You repeat and repeat that we must do this and must do that. I prefer to wait for some decent data and analysis by 3rd party authorities, and consider it folly to act in advance of these things. You are free to donate funds to charities that can put your ideas into action.

The California fires — an issue I am familar with — is poor evidence of the need for “policy action” to fight AGW, as they almost certainly result from normal climatic variation. Much of the American southwest is prone to long droughts. That you cite as evidence in the AGW debate re-enforces my point about the need for better understanding of these things before policy action.

I do not see that you have acknowledged — or even read — any of the points I have raised. This is not only discouraging, but also diminishes my confidence in what you say. I feel like I am talking with a cultist handing out tracts at the airport.

Fabius, I’ll quit repeating and simply thank you for hosting an interesting discussion and pointing to some interesting pieces to read. And yes, perhaps being a physicist (among other things) is a bit like being a cultist. Apart from that, I’ll look forward to seeing your thoughts in the other areas you cover.

Reply: Being a physicist is not at issue; your statement is hardly fair or reasonable.

You have made 10 comments, very polite but distinguished by an unwillingness or inability to respond to the data and reasoning given in either the post or the replies. Each comment ignores the reply and shifts to a new subject. This is a characteristic of cultists, even if you were Einstein. Also remarkable is that you do not explain the several instances in which your “replies” do not match anything said on this thread.

You repeatedly assert that policy action is needed, despite the deficiencies in pro-AGW case. To mention just a few: the inadequate quality control in the surface temperature data, cherry-picking when selecting of historical proxies, and the lack of outside review of the key computer models. These are serious critiques of the data and methods of the pro-AGW theories, none of which can be waved away with the “I’m a physicist” defense.

My comment about repeating was an invitation to provide a response, or point to some relevant analysis or data. Responding to nine comments with no sign that you have read them would tax the patience of a better man than I.

Should the government act before we understand the dynamics of AGW? Here is a historical case study.

The Black Death challenged the people and governments of that time to an extent beyond anything in our time. They responded with many strong measures. One was killing the dogs, suspected of causing or spreading the disease. This was easily done, but proved counter-productive. The dog’s fleas found new hosts, often people. Also, dogs were important in limitign the rat population.

Something similar happened recently in Sura, India (source). The equivalent today might be drastic measures to limit the growth of atmospheric CO2 — at great cost — while the Earth enters a cooling cycle. Action without understanding can have unpleasant results.

Fabius, my comment about being a physicist was in response to your comment about being “an airport cultist”. There is a perceptual change that occurs such as discussed by Gary Klein in “Sources of Power”. You have stated that you wish to wait for positive detection of “AGW” to believe in it. You point to critics of the data and processing of data leading to the IPCC claim of such detection.

That is a different kind of “skepticism” from that which is voiced by an atmospheric physicist such as Roger Pielke, Sr., who also has his differences with the IPCC. Pielke is claiming that the proper term should be climate change, not global warming because global warming is meaningless as to it’s effects on people, most of which are regional. Pielke does not criticize models for their lack of ability to obtain global numbers, but for their inability to make correct regional predictions. He criticizes the IPCC, not for believing in anthropogenic climate change, but for placing all the emphasis on curtailing greenhouse gas emissions while ignoring the climate effects of other anthropogenic activities. He looks, for example, at how deforestation in the Amazon can impact rainfall in the American midwest, an effect called a teleconnection. He points to his recent policy statement on the broader role that humans have in affecting climate. In short, Pielke is operating from a much broader range of data and experience than one can obtain from IPCC. I doubt that he would argue with the 2-3 deg estimate of global surface temperature change from doubling CO2, but would respond that such a number says nothing of the winners or loser or the response required from humans. Pielke also links, from several of his pages, to a National Research Council report on Radiative Forcing of Climate Change.

In short, both Pielke and I are operating from a different perspective than detection of global warming, which is, in our context, an interesting side-note to the effects of human activities. Our interest is more in the energetic driving of change and how various human activities create significant feedbacks. Pielke’s perspective is essentially one of human activities inescapably changing regional climates. His call is not for ignoring policy, but for broadening policy to deal with changes beyond trace gas emissions, in essence because anthropogenic climate change is inescapable.

This is a different perspective than the one that you profess, one coming from years of looking at terrestrial interactions and an understanding of how they constrain each other. It is also the manner in which someone like Pielke differs from Crichton.

Reply: Another change of subject. Every new comment ignores the replies, and drifts to another marginally related subject. That gives this dialog the “debating a cultist” tone.

(1) “This is a different perspective than the one that you profess, one coming from years…”

While this can be described as a different “perspective”, it is more accurately described as a different analytical question. Certainly an interesting and important one, but not relevant (except tangentially) to the question under discussion. It’s a big world, with many questions. This is why the comment policy asks that comments be related to the specific post. Unless the domain of a discussion is focused, I have found that discussions either collapse into mutually unintelligible babble — or just peter out from topic drift.

(2) “I doubt that he would argue with the 2-3 deg estimate of global surface temperature change from doubling CO2.”

As Steve McIntyre has noted so many times, that number is endless repeated in the climate sicence literature — but with very little analytical or empirical support.

For more information from the FM site

To read other articles about these things, see the FM reference page on the right side menu bar. Of esp relevance to this topic:

7 thoughts on “A discussion about global warming”

Good job, FM — tho Keith is doing a pretty good ‘true believer’ version of his side.

I’ve come to support gas taxes, both to reduce pollution (including CO2) and as a possible cushion for more stable prices, and to reduce income taxes.

The science for CO2 increases seems pretty strong. The science for what the effects of these increases are, seems much weaker. I understand that Antarctic ice is increasing — some nearby water is warmer, more water vapor, more snowing, more ice. It’s not clear such regional feedback loops are being modelled well, in the computer models.

It’s also not clear that such models understand why there was a Middle Ages warming, or a Little Ice Age. I won’t believe much in uncertain predictions of any global historical climate model that fails to reasonably explain the fairly well known not to distant past.

I understand that global cooling has happened fast, like within 100 years. But there are not cases of such fast global warming. (This could be the new first!)

The intellectual arrogance of the model builders is not to be trusted, neither in the case of no-longer ‘global warming’, nor in the low risk estimates of Credit Default Swaps. Nor in the simple low risk estimates for nuclear power risk — but I generally favor nukes with lots of safety. And I’m suspicious of any ‘environmentalist’ who is willing to support massive gov’t control of the economy to reduce CO2, yet opposes nuclear power.

Keith, if the crisis isn’t bad enough for YOU to strongly support nuclear power (safe in France, for instance), then I’m certainly not going to call it such a big crisis.

As my posts in the past indicate, I am not a supporter of “manmade” global warming but I have read every bit of information I can get, pro or con, and
have decided based on that. The problem I have is those on the other side don’t even bother to look at the counter information. It’s almost impossible to get them to admit that it even exists. Then they attempt to destroy the person and not the data. “Must of been funded by big oil” is a common attack.
The information should stand alone. If the data is good it will stand, if it’s not it will be disregarded. Thats the rational process to go through.
We seem to be lacking in that regard.

1)On a probability scale of -1.0 (certainly false) to 1.0 (proven true) where do you think the above statement resides?
2) At what probability level would you advise a policy maker to start mitigation efforts?
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.Fabius Maximus replies: (A) I do not do hypotheticals. I disagree with the premise, and so have no interest in the consequentes.

(B) The whole point of the skpetics case is that we lack the data to make these kinds of estimates. Obtaining this data should be a high priority for everyone on all sides of the debate.

* A network of surface temperature recording stations of low quality like this one gives us no useful data about climate trends.
* Global temperature data computed with poor quality control are useless as a basis for public policy decisions. See this and this; see this for a listing of such articles. Plus this describing one of the many oddities in the data.
* Computer models that do not adequately account for major factors like particulate emmissions and soot (see this for more information) are useless as a basis for public policy decisions.
* Work by scientists who refuse to release their data and methods — making outside review and replication impossible — has no place in public policy decisions. See these and these articles. Or this for a recent example.

I was tempted delete or severly edit this, citing the comment policy — clearly stated on the home page and at the end of every post: “please make them brief (250 words max).” At 3,073 words this is 12.3x the maximum length. This is longer than almost all posts on this site — longer than those on almost every site (except professional or subscription sites). It sets a bad precedent to allow this.

But I will do so just this once. But be warned, evil malefactors, that your transgressions against the FM site’s comment policy will no longer go unpunished! Since I do not have the time to edit them down, summary and swift justice will be done: deletion awaits your cursedly long comments!

It was not my intention to ask a hypothetical question. People make assessments in the face of uncertain data all the time. This is particularly true for those who make economic assessments (and suggest economic remedies!)

I was trying to obtain your overall assessment of the likelihood of AGW taking place. I interpret your answer to be that data (such as it is) does not give you reason to believe that AGW is happening. (and no reason to believe that AGW is not happening).

The second question was an effort to determine the threshold of certainty where action was warranted. I.e. what level of evidence is the right amount before we take action (strong possibility? balance of probability? preponderance of probability?)
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.Fabius Maximus replies: Let’s consider this in more detail. As you state, the context here is not an academic discussion, but making public policy (which has a different set of “rules”).

“Significant anthropogenic climate change is happening. … On a probability scale of -1.0 (certainly false) to 1.0 (proven true) where do you think the above statement resides?”

Probability can be calulated only when one has some minimum level of data, otherwise there is no point to the calculation. With AGW we have what appears to be both poor data quality and unverified models. Hence, no probability can be meaningfully caluated at this time. This is worse than using the Drake equation to calucate life in the universe. At least there the “model” (equation) appears reliable, even if we have little basis on which to estimate most of the parameters.

Keynes described this situation as follows (“The General Theory of Empoyment”, 1937, QJE):

By “uncertain” knowledge, let me explain, I do not mean merely to distinguish what is known for certain from what is only probable. The game of roulette is not subject, in this sense, to uncertainty; nor is the prospect of a Victory bond being drawn. Or, again, the expectation of life is only slightly uncertain. Even the weather is only moderately uncertain. The sense in which I am using the term is that in which the prospect of a European war is uncertain, or the price of copper and the rate of interest twenty years hence, or the obsolescence of a new invention, or the position of private wealth owners in the social system in 1970. About these matters there is no scientific basis on which to form any calculable probability whatever. We simply do not know.

Nevertheless, the necessity for action and for decision compels us as practical men to do our best to overlook this awkward fact and to behave exactly as we should if we had behind us a good Benthamite calculation of a series of prospective advantages and disadvantages, each multiplied by its appropriate probability, waiting to be summed.

He published those words in 1937, in the midst of a great depression. Fortunately we not are under such time pressure. Rapid mobilization of our resources could resolve many of the open questions quite quickly. Despite claims of urgency, only trivial and ad hoc measures have been take to do so far. For example, the Wegman and North Committees both worked with low budgets and great time constraints.

Our limits to effective action lie in our minds, in our resistance to overcome organizational constraints that prevent mobilizing our talent to answer these questions. The bureaucratic hurdles are high. NOAA and NASA (e.g., Hanson) do not want their data quality practices examined. Mann et al do not want their calculations checked (e.g., the cherry-picking of proxy data to produce the desired result). Many researchers do not want their proprietary data open for others use, despite it was often collected at public expense (e.g., Lonnie Thompson’s ice cores; see here).

We ask for this and much more before releasing a new drug onto the market. How much more should be done when the world is at stake?

I suspect that when this has been done the answer will be sufficintly clear that no fine slicing of probabilities need be done to determine the public policy implications.

Probability can be calculated only when one has some minimum level of data, otherwise there is no point to the calculation.

Nope. Probability, as a measure of one’s current belief about the future, a measure that can be usefully incorporated into decision making rules, such a probability needs no data.

Neither of your two referenced notes includes discussion of Bayes’ Theorem

As a formal theorem, Bayes’ theorem is valid in all common interpretations of probability. However, it plays a central role in the debate around the foundations of statistics: frequentist and Bayesian interpretations disagree about the ways in which probabilities should be assigned in applications. Frequentists assign probabilities to random events according to their frequencies of occurrence or to subsets of populations as proportions of the whole, while Bayesians describe probabilities in terms of beliefs and degrees of uncertainty.

However, I strongly agree with your view that more and better data should be collected, and all data analysis that is offered in support of one public decision or another should include full disclosure of the data, and all its likely imperfections.

As for Ael’s question, I’d answer that even if there was no AGW or, in the coming phrase ACC (climate change), the non-anthropogenic or ‘natural’ CC should be pushing human policy makers to mitigate the consequences. Thus, more flood control, dams, and water pricing (=conservation / sustainability) even without ACC.

However, huge anti-capitalist anti-carbon use taxes are not so good, tho I do support higher and slowly rising gax taxes.
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.Fabius Maximus replies: I find it fascinating when I (or others) quote from accepted texts (like Keynes in comment #5) and folks reply with statements like “Nope”.

Keynes’ framework for analysis of risk and uncertainty built on the work of others, most importantly Frank H. Knight‘s “Risk, Uncertainty and Profit” (1921). It is the foundation for modern risk management in a hundred fields.

There are other expert viewpoints on these things; see Wikipedia for some.

“Probability, as a measure of one’s current belief about the future, a measure that can be usefully incorporated into decision making rules, such a probability needs no data.”

The dice do not care what is my “current belief” about the physics of the craps table. Frequentists use “belief” in a technical sense as based on observations (watching dice or taking a poll). From the Wikipedia entry:

“Frequentists talk about probabilities only when dealing with well-defined random experiments.”

You confuse the related but distinct concepts of uncertainty and probability. That was the point Keynes was making — a core insight for the climate change debate.

How you think when the economic crisis will end? I wish to make statistics of independent opinions!
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.Fabius Maximus replies: It is vital to realize that reliable forecasts are not possible about the duration and severity of this crisis.

(1) The essence of the crisis is that it has few precedents; we are “off the map.”
(2) The outcome depends on policy decisions by governments which cannot be predicted, and on a larger scale by decisions of us — collectively and politically — which we cannot yet understand.

All that can be said IMO is that it will probably be long (2 – 5? years) and hard (worst since WWII).